In recent years, the viscous hypothesis and
other underlying physical assumptions of the viscous-plastic (VP) rheology
widely used in current climate and operational models have been revisited and
found to be inconsistent with the observed mechanical behaviour of sea ice. Other
studies have suggested that while the VP model can represent the mean global
drift of sea ice with a certain level of accuracy, it fails at reproducing some
key observed properties of sea ice deformation. We developed a new mechanical
model, named Maxwell-Elasto-Brittle, as an alternative to the VP rheology in
the view of accurately reproducing the drift and deformation of the ice cover
in continuum sea ice models. The model builds on a damage mechanics framework
used for ice and rocks. A viscous-like relaxation term is added to a
linear-elastic constitutive relationship together with an effective viscosity
that evolves with the local level of damage of the material, like its elastic
modulus. This framework allows the internal stress to dissipate in large, permanent
deformations along faults, or leads, once the material is highly damaged, while
reproducing the small deformations associated with the fracturing process and retaining
the memory of elastic deformations over relatively low damage areas. A healing
mechanism counterbalances the effects of damaging over large time scales.
Idealized simulations have confirmed that
the Maxwell-EB model reproduces the important characteristics of sea ice
mechanics revealed by the analyses of available ice buoy and satellite data: the
anisotropy of the deformation, the strain localization and intermittency, as
well as the associated scaling laws. Sensitivity analyses show that the model,
with few independent variables, can represent a large range of mechanical
behaviours, with both the persistence of creeping leads and the activation of new
leads with different shapes and orientations. Realistic simulations will be
presented, in particular, simulations of the flow of ice through Nares Strait.
These will demonstrate that the model reproduces the formation of stable ice
bridges as well as the stoppage of the flow, a common phenomenon within numerous
channels of the Arctic. In agreement with observations, the propagation of damage
along narrow arch-like kinematic features, the discontinuities in the velocity
field across these features, defining floes, and the eventual opening of
polynyas downstream of the Strait are all represented.

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